Avalanche Forecast

Issued: Nov 24th, 2017 4:58PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs and Loose Wet.

cgarritty, Avalanche Canada

Northwest Coastal.

Stormy weather is maintaining heightened avalanche danger in the region. This forecast is based on limited observations and demands a cautious approach combined with independent information gathering.

Summary

Confidence

Moderate -

Weather Forecast

Saturday: Cloudy with scattered flurries and 5 to 10 cm of new snow, increasing overnight. Light to moderate south winds. Freezing level to 600 metres with alpine temperatures of -5Sunday: Continuing flurries bringing approximately 5 cm of new snow. Strong south winds. Freezing level rising to 1000 metres with alpine temperatures of -2.Monday: Another round of flurries bringing 5-10 cm of new snow. Strong southwest winds. Freezing level to 1000 metres with alpine temperatures around -3.

Avalanche Summary

Reports from Wednesday included observations of several natural wind slab releases from steep, north-facing alpine terrain in Bear Pass. These were triggered by rain. Reports from Sunday showed evidence of a natural loose wet avalanche cycle focused on steep, low elevation rock slabs along Highway 16 between Terrace and Prince Rupert. Observations of high elevation terrain have been very limited. Please post your observations to the Mountain Information Network (MIN)

Snowpack Summary

Approximately 60 mm of precipitation fell over the region over the midweek storm, accompanied by moderate to strong winds and freezing levels of around 1100 metres. Under these conditions, rain saturated and eroded the snowpack at lower elevations while new snow accumulations of up to 60 cm blanketed the alpine. New snow depths are heavily elevation-dependant, with new snow depths below treeline ranging from 0 to 20 cm. Below the new snow, two weak layers are noted to have formed during the early season. (October 31 and November 11) Although their widespread presence is fairly certain, very few observations or tests of their reactivity exist. With that said, ongoing loading of the upper snowpack carries the potential to activate these deeper weak layers. Looking further to the north of the region near Ningunsaw, the snowpack is starkly different. Here, much drier, colder early season conditions produced a shallow snowpack composed mainly of weak, sugary snow. Snow depths in this part of the region are largely below threshold depths for avalanching.

Problems

Storm Slabs

Stormy weather is continuing to form touchy new storm slabs at upper elevations. Slab size and reactivity will increase with elevation. A storm slab release may have the potential to step down to deeper weak layer to produce a very large avalanche.

If triggered, storm slabs may step down to deeper layers resulting in large avalanches.The new snow will require several days to settle and stabilize.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Loose Wet

As snow stacks up at higher elevations, rain has saturated much of the snowpack below treeline. Danger from loose wet avalanches exists where surface snow remains moist - especially in steep terrain.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Be cautious of sluffing in steep terrain, particularly where the debris flows into terrain traps.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Nov 25th, 2017 2:00PM